1. Field of the Invention
The present invention relates to filters for medical equipment, such as medical suction canisters, and assemblies having filters for use with medical equipment.
2. Related Art
During operative surgery and other medical and biological procedures, suction canister systems are used to collect fluids, including blood, saline and other fluids. These fluids may accumulate during a procedure and must be removed, contained and disposed of after the procedure. A canister system may include a cylindrical canister closed by a cover or lid, and it may have an internal liner attached to the lid. Vacuum is applied to a vacuum port in the lid to develop a sub-atmospheric pressure or vacuum within the canister, which vacuum then also develops at the end of a collection tube connected to a patient port on the lid for suction. One such canister system is shown in U.S. Pat. No. 5,470,324, incorporated herein by reference.
The lid typically includes several access ports with associated attachment or connection elements. For example, the lid may have a large access port that typically remains capped until a fluid-setting agent is added. An outlet or "ortho" port on some canister systems has a wide riser portion for suction in orthopedic operations or for connection of a tandem tube from an additional collection canister. The vacuum port which pulls air from the canister has a float valve to prevent suction of fluid into the vacuum system when the fluid level in the canister gets close to the lid.
The vacuum for the suction canister system typically comes from a hospital or clinic vacuum pump through wall vacuum outlets in surgery suites or elsewhere. Because the vacuum system is common to a number of different areas throughout the facility, it is very important to insure that foreign objects, particles and fluids are not inadvertently taken up by the vacuum system. It is especially significant in fluid collection systems where fluids, or materials entrained in the fluids, may vaporize or become airborne under the influence of the vacuum system.
To stop or minimize possible contamination, a combination of filter elements have been used in the vacuum ports of suction canister systems. The combination of filter elements, commonly known as an aerosol trap, one type of which is included in Allegiance Corporation's canister systems under the trademark ITHAT.RTM., effectively stopped almost all fluid particles or airborne particles, preventing them from entering the vacuum system. (ITHAT is also an acronym for Integrated Two-stage Hygroscopic Aerosol Trap.) Consequently, the vacuum lines and the vacuum system as a whole were protected from contamination arising from airbornes getting into the vacuum system.
The aerosol trap is a combination of two discs of filter material positioned on each side of a polyethylene web or grid and held in place in the vacuum port by an apertured plug. The ITHAT.RTM. filter allows high flow rates while effectively trapping about 99.7 percent of the aerosolized microorganisms and particulates.
The aerosol trap can be assembled on the canister side of the vacuum port in a number of ways, but they all involve handling the two discs of filter material and the polyethylene grid individually. They are handled individually both when they are retrieved or collected for assembly and also when the discs of filter material and the grid are positioned in the underside of the vacuum port. The assembly process means that special attention is given to the process and also to later inspection to insure proper assembly. The assembly process is time-consuming and labor-intensive.